Twelve people have been found dead in police custody in the northern Nampula province of Mozambique.
Police said the causes of the deaths were not yet known but they promised to launch an investigation.
The 12 were among 29 detainees accused of instigating violence this month in which two Red Cross workers died.
Two policeman were also killed when a mob attacked as rumours spread that health workers were responsible for spreading cholera in the region.
The district administrator, Bernardo Adriano, was quoted in the state media as saying that the prisoners might have attacked each other.
Human rights organisations have long accused the police in Mozambique of keeping prisoners in over-crowded cells under deplorable conditions.
Chlorine in wells
In Saturday's violence at the village of Quinga, five other Red Cross employees were seriously injured and 33 workers fled the area, the organisation said.
It is reported that when a cholera victim died, bereaved villagers concluded the Red Cross was spreading cholera in the wells, when they were in fact adding chlorine to decontaminate the water sources.
A police statement on Tuesday said 29 people had been detained for questioning following the violence.
Later, a prison official, Floriano Sumane, was quoted on state radio as saying he had received information from police that 12 of the suspects died early on Tuesday during violence inside the cell they shared.